1. Field of Invention
The present invention relates to the fields of near infrared spectroscopy (NIRS) and its application to the field of Urology and more specifically to bladder urodynamics and in the diagnosis of disorders related to voiding dysfunction.
2. Description of Related Art
Voiding dysfunction affects over 50% of the population. A primary tool used to understand how the bladder functions is to test bladder urodynamics. Urodynamics can measure bladder volume, whether the bladder has normal sensation during filling and whether the bladder contracts with appropriate strength when a patient/subject voids. Urodynamics testing can also inform us if a patient has an obstruction to the bladder or, if there is leakage of urine (incontinence—involuntary leakage), then what type of leakage it is. Urodynamics are done to diagnose a variety of underlying problems of the bladder. It is also used following implementation of treatment strategies to demonstrate success or failure. A traditional urodynamic test consists of three components—the non invasive uroflow (which gives information about bladder emptying), the Cystometrogram (which gives information about bladder filling) and the pressure flow study (which gives additional information about bladder emptying).
To perform standard urodynamics, the patient is asked to attend with a full bladder. The patient is asked to void onto a scale, which produces a tracing of how quickly they can void, and the total voided volume. Then, two catheters are positioned, one in bladder and one in the rectum. From this point onwards the test is invasive in nature. Furthermore, the presence of the catheter in the urethra is a known confounding factor because the catheter itself can cause obstruction to voiding, can be irritating to the bladder causing false contractions, and/or can have side effects including bleeding and infection.
It is also useful for Urologists to have a direct measurement of how strong the bladder muscle itself contracts. To do so, a catheter is placed into the rectum and it is connected to a pressure transducer that measures abdominal pressure. A second catheter is placed into the centre of the bladder via the urethra and is also connected to a pressure transducer. It is known that the pressure in the centre of the bladder is a reflection of the abdominal pressure plus the pressure generated by the bladder muscle itself. Therefore, it is possible to calculate the pressure generated by the bladder muscle indirectly. However, conventional urodynamics testing does not provide a direct measure of bladder muscle activities. This deficit is apparent when the flow of urine is measured without the use of catheters. The volume of urine voided onto a scale provides a tracing of how quickly the volume of urine is voided. This is called the ‘non invasive uroflow’. However, with uroflow testing no information is recorded from the bladder muscle. Both a weak bladder muscle and an obstructed bladder with high pressure in the bladder muscle wall can produce a dribbling type of urinary stream with reduced flow rates.